This invention relates to viewing latent magnetic images; and, more particularly, to apparatus for viewing latent magnetic images.
Microfilm viewing apparatus have long been utilized in the storage and retrieval of information as a compact, convenient alternative to the storage of papers commonly referred to as "hard copy".
There has recently been introduced a magnetic imaging system which employs a latent magnetic image on a magnetizable recording medium which can then be utilized for purposes such as electronic transmission or in a duplicating process by repetitive toning or transfer of the developed image. Such latent magnetic image is provided by any suitable magnetization procedure whereby a magnetized layer of marking material is magnetized and such magnetism transferred imagewise to the magnetic substrate. Such a process is more fully described in U.S. Pat. No. 3,804,511 to Rate et al.
The latent magnetic image, by way of analogy to xerographic imaging, is usually developed with a magnetic developer to render the latent magnetic image visible. The developed, visible, magnetic image is then typically transferred to a receiver such as, for example, a sheet of paper to produce a final copy or print. This final copy or print is typically referred to as hard copy.
In addition to making hard copy, there is also interest in novel compositions and techniques useful for rendering latent magnetic images visible. For example, U.S. Pat. No. 3,013,206 to Youngquist et al. discloses a magnetic reader comprising a hollow non-ferromagnetic vessel having a cavity field with a suspension of flat, visible, weakly ferromagnetic crystals which orient when suspended in the liquid and in response to a magnetic field.
It is desirable at times to store information as latent magnetic images which can be reviewed in visible form to retrieve information visually and/or select appropriate information for development into hard copy.